1. Field of the Invention
The present invention relates to an ejector, an ink jet cartridge, ink jet printing apparatus and ink jet head kit having such an ejector, an ink jet printing method using such an ejector, as well as printed products obtained by employing such a method or apparatus. More particularly, the present invention relates to method and apparatus for printing by ejecting an ink and a liquid for improving the printability of the ink on a material to be printed. Further, the present invention relates to an ink ejector for ejecting an ink or a printability improving liquid for use in an ink jet printing apparatus or method and to an ink jet cartridge for use in an ink printing apparatus.
The present invention is applicable to apparatuses which applies an ink onto a printing material, i.e., a medium on which printing is performed, such as cloths, threads, leathers, nonwoven fabrics, OHP paper, metal, glass as well as commonly used general paper. Specific examples of such apparatuses include business machines and apparatuses such as printers, copiers, and facsimiles, and large scale production systems and industrial production machines and apparatuses, such as textile printing apparatuses.
2. Description of Related Art
Printing apparatuses having functions of printers, copiers, facsimiles, and the like or printing apparatuses used as composite machines inclusive of computers, word processors, and the like and output machines and apparatuses for work stations are constructed so that images including characters, symbols, etc. can be printed or recorded on a printing material or printing medium (material to be printed) such as paper, plastic thin plates (sheets for OHP, etc.) based on image information. The printing apparatuses may be classified into ink jet type, wire dot type, heat-sensitive type, thermal transfer type, laser beam type, and so on depending on the type of printing by the printing means used.
In a printing apparatus of the serial-type in which main scanning is performed in the direction crossing the direction in which a printing material is transferred (sub-scanning direction), printing is performed as follows. First, after a printing material is set to a predetermined printing position, images inclusive of characters, symbols, etc. are printed by the printing means mounted on the carriage which moves along the printing material (main scanning) until printing for one line is completed. Then, a predetermined amount of paper is fed (sub-scanning), and then images for next line are printed. This procedure is repeated until images are printed over a desired area of the printing material. On the other hand, in a printing apparatus of the line type in which printing is performed by sub-scanning, i.e., feeding a printing material in the direction of transferring a printing material, the printing material is set to a predetermined printing position and printing for a whole line en bloc is performed continuously, while feeding a predetermined amount of paper or printing material (pitch feeding), so that images can be printed over the whole predetermined area of the printing material.
Among the printing apparatuses, a printing apparatus of the ink jet type (ink jet printing apparatus) ejects ink on a printing material from a printing means (printing head). The ink jet printing apparatus of the type has various advantages in that it is easy to make the printing means compact in size, it can print high precision images in high speed, it can print on normal paper without resort to any special treatment, it runs at a low cost, it works with less noises since it is of the non-impact type, and it allows printing color images using multiple color inks. Of these, much higher speed printing can be attained with the line-type printing apparatus which uses a line-type printing means having an array of a number of ejecting ports arranged along a direction of the width of paper.
In particular, it is advantageous to use a printing means (printing head) of the ink jet type which ejects an ink making use of thermal energy since it is possible to readily manufacture one having an arrangement of liquid passages or ejecting ports or orifices at a high density, thus facilitating further reduction in size, by forming on a substrate films of an electrothermal transducer, electrode, liquid passage wall, a top plate, and so on. Also, utilization of the advantages of IC technology and micro-processing technology, makes it easy to fabricate a printing means in a longer form or in a planar form (two-dimensional structure) and to modify the printing means into the so-called full-multicolor type one which enables full-line type printing in multiple colors and to mount the printing means on a printing head or a printing apparatus at a high density. On the other hand, there have been various requirements for the material of the printing material. Recently, there has been an increasing demand for use of thin paper, processed paper such as punched paper for filing, seamed paper, paper having a desired non-standardized size or form, or the like in addition to usual printing materials such as paper and resin thin plates.
As described above, the ink jet printing apparatus is used widely as a printing apparatus such as a printer, a copying machine because of its low noise, low running cost, ease of down sizing, ease of arrangement for multi-color printing construction. However, in the case where images are printed on a so-called normal paper as a printing material by one of these printing apparatuses of ink jet printing type, sometimes images have insufficient water resistance, or when printing color images is contemplated, high concentration images that cause no feathering do not stand together with images that cause no blurring among the colors. Thus, it is difficult to obtain durable, high quality color images.
In order to increase water resistance of images, there is used a printing method which employs an ink containing a coloring material having a resistance to water. Recently, such a method has been put into practice. However, the water resistance is yet insufficient, and the ink in principle is difficult to be dissolved in water once it is dried so that the ejecting ports of the printing head tend to be clogged. Naturally, in order to prevent such a clogging, the printing apparatus requires complicated arrangements.
Japanese Patent Application Laying-open No. 84992/1981 discloses a method for preparing a large amount of a printing paper by coating a material for fixing a dye in an ink to be used on a printing paper in advance prior to printing with the ink. However, this method have various disadvantages in that it is necessary to perform printing using the special printing paper thus prepared in advance, and the precoating of a printing material with a material for fixing the dye inevitably results in a need of employing a larger apparatus for preparing a special purpose printing paper on a large scale and in an increase in cost, and further, it is difficult to coat the above-described material for fixing the dye on a printing paper in a predetermined film thickness uniformly upon preparing the special purpose printing paper.
Japanese Patent Application Laying-open No. 63185/1989 discloses the technology in which a colorless ink for insolubilize a dye is deposited on a printing paper by means of an ink jet printing head. Japanese Patent application Laying-open No. 202328/1993 discloses technology for obtaining water resistant images without color bleeding by applying on a printing paper a solution of a polyvalent metal salt solution and then an ink containing a chemical dye having a carboxyl group. However, as in these technologies, in the case where the solution which insolubilizes a dye is ejected by an ink jet printing head, a problem arises in that the printing apparatus comes to be out of order when the printing ink and the solution for the insolubilization of the ink come into contact each other in the body of the apparatus. There is no teaching or suggestion in the prior art on the arrangement of printing apparatus that have overcome such a problem.
Further, many technologies have been disclosed that increase the durability of images on the printing material. Japanese Patent Application Laying-open No. 24486/1978 discloses the technology in which the printed material is post-treated to convert the dye into a lake and have it fixed in order to increase the moisture durability of the printed material. In particular, Japanese Patent Application No. 43733/1979 discloses the printing method in which two or more components are used whose film-forming properties increase at a normal temperature or upon heating when they are contacted each other. According to this method, there can be obtained printed materials having formed a strongly bonded coating by the contact of the components on the printing material. Japanese Patent Application Laying-open No. 150396/1980 (Japanese Patent Application Publication No. 38155/1987 discloses the printing method in which after ink jet printing is performed using an aqueous dye ink, there is given a water resistance-imparting agent which forms a lake with the dye.
U.S. Pat. No. 4,538,160 discloses an ink jet printing method in which the position of an image to be printed is discerned in advance and a printing ink and a processing ink (liquid for improving the printability of the ink) are applied one over another. Various variations are disclosed. For example, prior to the application of a printing ink, an image may be formed with the processing ink. The processing ink may be applied over the image previously formed with the printing ink. Or, first the processing ink may be applied to form an image, then the printing ink applied over the image with the processing ink, followed by applying again the processing ink over the image. However, the above-described Japanese publications fail to disclose in substance recovering means for maintaining reliability of ejection, head structure, tank structure, printing mode for increasing the quality of printed images, which are specific to ink jet printing apparatuses.
On the other hand, ink jet printing methods by nature have the following problems. First, since printing is performed by ejecting ink droplets from a printing head onto a printing material such as paper or OHP film, fine ink droplets (mist) generated in addition to the ejected main ink droplets and ink droplets rebound on the printing material adhere on the surface of each ejecting port plane which is provided with ejecting ports and the ink accumulates in large amounts around the ejecting ports or foreign matter such as paper powder, etc. adheres thereto, resulting in that normal ejection of ink is prevented so that the ink is ejected in an unexpected or undesired direction (distortion), or ink droplets are not ejected (non-ejection).
Next, after the non-printing condition is continued for a prolonged period of time and the printing head has not ejected for a long time, the ink in the ejecting ports evaporates and dries so that the thickened or solidified ink clogs in the ejecting ports to cause an ejection failure such as a distorted ejection or a non-ejection. For this reason, ink jet printing systems are each provided with a recovering means.
As a means for wiping out unnecessary ink and foreign matter such as paper powder on the surface of an ejecting port plane due to the above-described mist or rebound ink droplets from the printing material, a recovering means is generally adopted which has an arrangement in which the surface of the ejecting port plane is wiped with a blade made of an elastic material such as rubber. When the surface of the ejecting port plane of the printing head is wiped with a blade, the ink naturally adheres to the blade. In a printing apparatus having two or more printing heads arranged side by side and allowing color image printing using different color inks, an ink which adhered to the blade in wiping the first printing head mixes with another ink of a different color which adhered to the blade during the wiping of the second printing head for a different color ink than the color of the first printing head.
The following contents relate to technical themes discovered by the present inventors during the development in Canon Kabushiki Kaisha, and unknown publicly.
In a printing apparatus having mounted thereon a printability improving liquid ejecting head which ejects a solution that solubilizes or agglomerates the dye or coloring material in the ink (printability improving liquid), wiping the printing head and the printability improving liquid ejecting head with the same blade results in mixing of the ink with the printability improving liquid on the blade or on the ejecting port plane of the printing head. As a result, the wiping leads to clogging of the ejecting ports with the solubilized or agglomerated coloring material (dye), thus causing non-ejection frequently, so that most of the ejecting ports fail to eject the ink normally. It has also been found that when the non-ejection of the printability improving liquid occurs frequently, the water resistance of the images deteriorates partially or sometimes unevenness of the images occurs.
That is, it has been found that at the time of wiping, the ink or printability improving liquid rubbed off contact each other on the blade or on the ejecting port planes, and the insolubilized or agglomerated dye adheres to or clogs the ejecting ports to generate a distorted ejection or non-ejection of ink. Further, it has been found that in the case of a color ink jet printing apparatus, wiping a plurality of printing heads with only one blade increases the amount of inks which adheres to the blade and causes contamination of inks, thus giving more adverse effects.
In an ink jet printing apparatus, the following construction is generally adopted in order to overcome the problems of a distorted ejection or non-ejection caused by the evaporation and drying of ink in the ejecting ports. That is, the printing head is closed with a cap at the time of non-printing to prevent the evaporation and drying of the ink in the ejecting ports, which results in the thickening or insolubilization of the ink. If the ink thickens or solidifies to cause ejection failure, or if there exists foreign matter which has not been removed with the blade, the thickened ink in the ejecting ports and the foreign matter on the surface of the ejecting port plane together with the ink are sucked and discharged using a suction pump connected to the cap so that a normal ejection state can be recovered. The ink or printability improving liquid discharged is absorbed by an absorber for waste ink disposed in the body of the printing apparatus through a tubing arranged in the downstream of the suction pump.
For example, if the pump for the suction and recovery is used commonly for various inks (printing ink or inks and printability improving liquid for the ink or inks) as in the conventional techniques, the ink or inks could insolubilize in the pump to cause disorder of the pump. Further, the ink agglomerate or insolubilizes in a waste ink tank for storing a waste ink or inks, a porous absorber contained in the waste ink tank decreases in its absorbability, so that leakage of ink tends to occur.
In the arrangement in which a liquid which insolubilizes the dye in an ink is ejected by the ejector of an ink jet printing apparatus, there is a fear that the ink and the printability improving liquid come into contact and mix with each other, and in that case the insolubilization of the dye in the ink could bring the printing apparatus into disorder or cause its failure. For example, problems relate to real ejection and preliminary ejection, respectively. Both the problems affect the quality and efficiency of printing to a large extent.
In the printing action of the on-demand type ink jet printing apparatus, not all of a plurality of ejecting ports provided in a single printing head is always used. There are some unused ejecting ports that have not been used for at least a certain period of time. In the case of a color printing apparatus having a plurality of printing heads, there may be the case where the whole printing head to which no data is transferred (which does not print) is unused. If the carriage is scanned or stopped with the surface of the ejecting port plane being uncapped, the ink on the ejecting port plane or in the ejecting ports, of which no ejection of ink continues for a predetermined time, evaporates and dries, thus causing a decrease in the ejection ability and a decrease in the quality of printed images.
To prevent such undesirable phenomena as described above from occurring, an ink jet apparatus generally performs an ejection of ink at a predetermined position at a predetermined time interval regardless of whether or not printing data are transmitted so that the ink in the ejecting ports can be discharged and replaced by fresh ink and the ejection can always be maintained in a proper state. Such an action of ejection of an ink is called a "preliminary ejection". The ejected ink discharged by the preliminary ejection is directed toward a cap arranged in a recovering unit or discharged toward a location called a "preliminary ejection position" arranged separately in order for the ejected ink not to scatter onto the printing material or in the printing apparatus and generate a contamination. However, if the pump at the preliminary ejection position is used commonly for the ink and the printability improving liquid, the ink is insolubilized and deposits in the pump to sometimes cause a discharge failure.
The ejected ink ejected by the preliminary ejection is ejected in a cap in an ejection recovering unit or an ink receiver arranged separately from the cap, and finally is stored in a waste ink tank or a waste ink absorber so that it does not scatter on a printing material or in the body of the printing apparatus and contaminate them. However, in the arrangement in which the preliminary ejection is carried out in a cap, it is necessary to suck the ink which accumulates in the cap by the preliminary ejection, and an action such as a displacement of the printing head for the suction is performed, which results in a decrease in throughput.
Provision of separate ink receivers for receiving the ink ejected by the preliminary ejection could solve such a problem as described above. However, if the ink and the printability improving liquid which agglomerates or insolubilizes the coloring material such as the dye contained in the ink are ejected in one and the same ink receiver, agglomeration of the coloring material occurs within the receiver, and in addition evaporation and thickening of the ink clogs the waste ink passage communicating from the ink receiver to the waste ink tank so that the ink received at the time of the preliminary ejection cannot be discharged and to be worse the ink or the printability improving liquid overflows from the receiver to cause a contamination of the inside or body of the printing apparatus.
FIGS. 1A, 1B and 1C schematically illustrate the clogging of a waste ink passage.
In the arrangement in which an ink and a printability improving liquid are ejected into a single ink receiver 400, the ink and the liquid mix with each other on a wall of the ink receiver 400 to cause an agglomeration of the ink to deposit an agglomerate 405, which grows bigger and narrows the liquid passage as shown in FIG. 1B until it clogs the entire liquid passage as shown in FIG. 1C, resulting in that the ink cannot reach a waste ink absorber 411 contained in a waste ink absorber 410. If the preliminary ejection is performed toward the ink receiver in such a clogged state as described above, portions of the ink and liquid that are not contained in the ink receiver overflow in the inside of the printing apparatus and contaminates it.
Further, in an ink jet printing apparatus provided with a plurality of ejectors, mist generated from one ejector would adhere onto the surface of an ejecting port plane of another ejector. In particular, mist generated by an ejector preceding in the direction of scanning of the carriage tends to adhere to another ejector that follows the preceding one.
As described above, the arrangement is generally adopted in which the ejecting port plane is wiped with a blade made of an elastic material such as rubber in order to remove or wipe off an unnecessary ink on the ejecting port plane around the ejecting port due to the mist and rebound ink droplets from the printing material as well as foreign matter such as paper powder.
However, once mists of the ink and printability improving liquid adhere onto the ejecting port planes of the ejectors for the ink and the liquid, there occurs insolubilization or agglomeration of the coloring material in the ink so that not only it is difficult to remove with a blade but also there arises a problem of ejection failure.
FIG. 2 is a schematic perspective view showing an outline of the construction a conventional ink jet printing apparatus. FIG. 3 is a schematic diagram illustrating the wiping action of the blade in the printing apparatus shown in FIG. 2. In FIGS. 2 and 3, a printing head 1003, which ejects an ink from a plurality of ejecting ports provided in a surface 1001 of an ejecting port plane and prints an image on a printing material 1002 (printing medium such a printing paper), is mounted on a carriage 1004 with alignment. The carriage 1004, supported by a guide shaft 1005, moves to and fro along the guide shaft 1005 which guides the direction of the movement of the carriage 1004, facing the printing material 1002. The printing material 1002 is transported (fed) according as transfer rolls 1007 and 1008 rotate. The printing material 1002 after printing is discharged out of the printing apparatus by discharge rolls 1009 and 1010.
The foreign matter such as paper powder or ink droplets which adhered to the surface 1001 of the ejecting port plane of the printing head 1003 are removed or wiped off by a wiper (wiping member) 1006 positioned outside an image forming region (printing region). At a position outside the printing region are provided caps 1011 for covering the surface 101 of the ejecting port plane to prevent drying of the ink in the ejecting ports or clogging of the ejecting ports, or for absorbing and discharging the ink from the ejecting ports by means of a pump, etc.
Hereinafter, the action of the wiper 1006 for wiping or cleaning the surface 1001 of the ejecting port plane of the printing head 1003 will be described. In FIG. 3, the conditions a, b and c of the wiper 1006 indicate the states of before a wiping action, during a wiping action, and after a wiping action, respectively. When the carriage 1004 moves in the direction indicated by the arrow A, i.e., from the right to the left in FIG. 3, the printing head 1003 mounted on the carriage 1004 also moves in the same direction as above. According as the printing head 1003 moves, the tip portion of the wiper 1006 is urged in flank and bent so that the tip portion moves while being pressed against the ejecting port plane 1001 at a proper pressure.
In other words, since the printing head 1003 moves (or passes) with the wiper 1006 being bent and pressed thereagainst, the foreign matter or ink adhering to the surface 1001 of the ejecting port plane is wiped off by the tip portion of the wiper 1006. After the printing head 1003 has passed completely, the wiper 1006 reverts to the original shape (upright figure as shown in FIG. 3, the condition c) due to its resilience. Cleaning the surface 1001 of the ejecting port plane by a series of the above-described wiping actions allows ejection of an ink to occur in a proper state stably so that high quality images can be printed.
However, the ink jet printing apparatus using in combination the cleaning means for cleaning the surface of the ejecting port plane with a wiper and the technology of using a printability improving liquid for improving the printability of the ink and having a head for ejecting the printability improving liquid has the following three technical problems. Firstly, after repeated wiping, the ink and the printability improving liquid adhere to the wiper and their reaction product fixes thereon so that the wiping ability of the wiper decreases gradually. As a result, the unnecessary matter adhering to the surface of the ejecting port plane cannot be removed sufficiently, thus causing a distorted ejection or an ejection failure to finally deteriorate the quality of printed images.
Secondly, in case the liquid ejecting head and the ink ejecting head are to be cleaned successively, the printing head has to be cleaned just after the liquid ejecting head is cleaned, since one wiper cleans both the liquid ejecting head and the ink ejecting head, with the printability improving liquid remaining on the surface of the wiper, resulting in that the liquid reacts with the ink to for a reaction product which fixes on the ejecting port plane. This causes an ejection failure, and at worst, a recovery of the heads becomes impossible even by the use of the above-described recovering means.
Thirdly, when two wipers are driven in accordance with the liquid ejecting head and the ink ejecting head, it takes a longer time to complete wiping and the printing speed of the printing apparatus decreases. However, none of the prior art references does teach or suggest a recovering means or the like which solves the technical problem on the ejection of an ink that is specific to ink jet printing apparatuses and which allows the maintenance of reliability of ejection of an ink and the maintenance of performance of the printing apparatus.
As described above, the prior art referred to above fails to teach or suggest disorders occurring in the printing apparatus due to the fixing of an ink with a printability improving liquid for improving the printability of the ink and arrangement for solving the problem.